Updated: Jan 31, 2022
Q: Why do trainers recommend food rewards?
A: The majority of dogs enjoy treats. It's what treats are designed for, after all. If your dog doesn't enjoy it, the maker of the treat failed your dog (hahaha). As us trainers don't often talk to people on what rewards they should use for their specific dog, we go with what the majority of dogs enjoy (food). There are other reasons, though.
In group class, the instructing trainer is trying to keep a room of humans and their dogs on the same page at the same time moving at (roughly) the same speed. If Joe the Golden Retriever is being rewarded with ten seconds of ball time and Lily the Cocker Spaniel is being rewarded with a soft treat that she eats within a second, Joe quickly falls behind Lily because it takes him longer to get the full reward experience (not to mention his humans need to get the ball back without accidentally punishing him). It's not a question of which reward is "better". In group class, it's a matter of keeping the class together so that all dogs have the same amount of practice under the watchful eye of the trainer.
It's also a matter of keeping your dog focused on the training. Joe, from the above example, is super interested in keeping his ball. He loves his ball. It's the best thing in the world to him (aside from all the other best things in the world). He doesn't want it to go away, unless someone's starting a game of fetch and that's another best thing. If his humans aren't careful how they get the ball back, taking the ball could be a small punishment when Joe didn't do anything wrong. Because he didn't do anything wrong, he loses interest in what's going on because he just got punished and now he wants to leave. Or, maybe his humans do get the ball back without accidentally punishing him, but now all his attention is on the fact that they have a ball and he wants it and it's in the pocket if he could just grab it out and his humans sound like the adults in a Charlie Brown comic. His attention is no longer on training. He wants to play. Lily, on the other hand, ate her treat while still focusing on her humans and her humans never lost her attention.
At home, when it matters less if you keep your dog's attention on training because there's no time schedule or restraint, feel free to use whatever things or experiences your dog enjoys... just don't get upset when Joe runs away with the ball.
Q: What can I do about my dog eating poop?
A: This is a complex one. There are a couple medical conditions that can cause coprophagia (the scientific term), so it's always a good idea to make your veterinarian a first stop (when you set up the appointment, ask if you should bring a sample). Your veterinarian may also ask you what you're feeding your dog and how much, as some foods may be too digestible and go through your dog's digestive system too quickly, leading to malabsorption and your dog trying to get the nutrients the second time around. Too little food can also cause your dog to try to get more nutrients any way they can. Your vet may give you (or tell you where to find) products meant to aid your dog's digestion or make the stools less palatable and sometimes this (and maybe a diet adjustment) is enough to eliminate the problem.
Nursing mothers naturally eat their puppy's stools. This is completely normal and typically ends when the puppies are weaned and start to leave the den/whelping box.
From a training perspective, the main focus should be on management. If your dog starts investigating poop, give them a known cue/trick to do in order to interrupt the investigation. You should pick up your dog's poop as soon as it happens and while your dog is distracted by something (for example, they poop, you throw a treat on the ground for them to find as you pick up the poop). This also means predicting when your dog will poop. Dogs typically eliminate a set amount of time after a meal, so a feeding schedule can assist knowing your dog's elimination schedule. Some dogs, especially if they're confined alone for too long or in too small an area, pick up coprophagia as a boredom relief. It's something to do. In these cases, you can give your dog interactive toys, puzzle toys, new/different toys or chews, or you can hide food for your dog to find to help stave off boredom. Remember that, for whatever reason, your dog believes that eating poop will accomplish something. Make it so your dog does not need to reach for poop to accomplish that goal.